Information I have on oscillators/tolerances & pricing aligns well with yourfindings. Although there may be up to a 2-3x price factor between 100 & 20ppm parts, the absolute difference is in the 'used hubcap' realm. Somethingthat could be washed out over time with the large volumes of Ethernet ports.

Cross-linking to Henning's thread on reference clocks, I could then envisagea 10GE LAN PHY card with a 156.25M +/-100ppm crystal or a 10GE WAN PHYcard with a 155.52M +/-20ppm crystal. I'm wondering what your view is for adual-mode UniPHY card. Obviously a 20ppm crystal also satisfies the LAN spec,but a 730kHz swing is more than a crystal can be tuned, so it sounds like bothoscillators would be needed. That's about an extra square inch of board space, etc.Thoughts?

I appologize for the delay in responding to your question. I wanted tobe absolutely sure of the facts before I replied.

I have sent out 5 requests for quotes for oscillators, and thus far Ihave received three responses.

The first two responses indicated a less than 10% price premium for a20 ppm 155.52 MHz oscillator versus a 100 ppm oscillator with otherwiseidentical specs. I can't talk about absolute price on this reflector,but I can say that the price difference is very small. Truly, it islost in the noise as far as the overall cost for a 10 Gigabit interfaceis concerned.

The third quote I received indicated a more substantial costdifference. The 20 ppm oscillator cost twice as much as the 100 ppm.However, the lead time for the 100 ppm oscillator was 20 weeks, whereasthe 20 ppm oscillator is available immediately. Once again, theabsolute price difference is a very small percentage of the overallcost for a 10 Gigabit adapter.

My conclusion remains the same. Specifying 20 ppm is the right way togo. The cost difference does not justify changing to 100 ppm, becausethis change probably will compromise compatibility with existing OC-192transponders and regenerators.

As to the jitter specifications, it is my understanding that the WANPHY proponents want to use all of the same optical components that arebeing specified for the LAN applications of 10 Gigabit Ethernet. Ibelieve that the SONET jitter specifications do impose additional coston the optical components. It is unreasonable to burden the LANapplications with the cost of meeting the SONET jitter specifications.Therefore, while I am keeping an open mind on the topic, and I amwilling to consider other points of view, I believe that we should notimpose the SONET jitter specifications on the 802.3ae PMDs, and I don'tthink that this will compromise compatibility with OC-192 transpondersand regenerators.

If I get any additional responses to my requests for quotes, I willbe happy to share them on the reflector.

You mention that the "cost difference between +/-20ppm and +/-100ppm oscillators is a tiny fraction of the total cost of a 10GigE interface".Could you perhaps substantiate this statement with quantitative input (some real numbers). My understanding is that the +-100ppm tolerance was specified only to keep the cost down (as the cost differential between a 20ppm solution and 100ppm solution is perceived to be significant).